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Thread: 347 Idle Hunting

  1. #1
    Join Date
    Dec 2013
    Location
    Oklahoma
    Posts
    174

    Default 347 Idle Hunting

    I've had the Terminator (V4) on my '66 Mustang 347 Stroker since early 2014. I'm running the Ford TFI computer controlled timing. 10° Crank Timing. 18° idle timing. The car runs great, but I've had hunting RPM immediately after starting the engine at operating and sub-operating temps (for YEARS). This doesn't happen every time and the RPM fluctuate between 300-500 RPM for ~3 seconds right after the car starts. I don't have any issue getting the car started normally. I've tried addressing this in the past, but after several datalogs and trial & error, it hasn't gone away. I'm now back at it and. Here's what I have tried one at a time:

    - Adjusted IAC Parked Position
    - Adjusted Cranking Fuel
    - Adjusted P & D Term Idle Spark
    - Changed the Advanced Idle Control to Slow
    - Adjusted After Start Enrichment
    - Startup IAC Hold Time
    - RPM Above Idle To Re-Enable Idle Control

    I turned Closed Loop off to see how it reacted and I had one datalog that was good and a second that hunted. I have a good Global File and recent datalogs showing all of the symptoms as well as a normal after start if someone can look at them if I email them over. Any feedback and direction would be much appreciated.
    Last edited by 66FSTBK; 05-05-2019 at 03:41 PM.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    21,585

    Default

    Temporarily block off the IAC air inlet port with a strong piece of tape, to determine if it's the problem (or the IAC programming). Then we'll have more to work with.
    Incidentally, the small block Ford is particularly sensitive to the IAC control programming, which is why I'd like the results from this test. It's an easy test to do.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3
    Join Date
    Dec 2013
    Location
    Oklahoma
    Posts
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    Default

    Thanks, I’ll try that. Does it matter if the engine is cold or hot?
    EDIT: Car wouldn’t start cold with IAC port blocked. Placed tape over port at operating temp while running and it ran fine, but I could tell it affected the idle a bit. AFR was still normal. Car won’t start with port taped off at operating temp.
    Last edited by 66FSTBK; 05-05-2019 at 11:15 AM.

  4. #4
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    Location
    Connecticut
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    Default

    Oh, I misunderstood the problem. I thought you had an idle problem, not related to startup (momentarily after startup). Disregard my post #2. Try this:

    Typical IAC Control/Ramp Down Parameter Settings
    Advanced Idle Control: ......................... Slow (Usually the best control.)
    IAC Type: .......................................... Stepper (4-wire), PWM (2-wire)
    IAC Hold Position: ................................ 10%-30% (Usually 15%-20%.)
    Ramp Decay Time: ............................... 1.0-3.0 sec (Usually 2.0 sec.)
    RPM Above Idle To Start Ramp: .............. 1000 RPM (Or higher.)
    RPM Above Idle To Re-enable Idle Control: 50-200 RPM (This setting can be finicky.)
    Startup IAC Position - Hold & Decay Time: 1.0-1.5 seconds (Less is typically better than more.)
    Not IAC, but Idle Spark control usually works well at: 30-40 P Term & 50-60 D Term.
    http://forums.holley.com/showthread....neral-IAC-Info (General IAC Information - Read "IAC NOTES")
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5

    Default

    I've seen this happen with too much target A/F Ratio Offset for colder coolant temps. It's a "rich roll". You honestly don't need to Offset it much if at all.

  6. #6
    Join Date
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    Connecticut
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    Default

    I agree. Read about the A/F Ratio Offset table here: http://forums.holley.com/showthread....6254#post36254 (Good Starting Advice Thread - Especially posts #2, #4 & #6.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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